Ultra-low sulfur fuel compositions containing organometallic additives

ABSTRACT

A method, apparatus, and fuel composition for the protection of a catalytic after treatment system and a method for protecting a catalytic after treatment system in a low sulfur fuel system are discloseD. A scavenging agent is introduced into the base fuel in an amount effective to complex with catalytic poisoning combustion by products and reduce catalyst poisoning. In a preferred embodiment, the scavenger is an organometallic compound which also imparts additional desirable properties to the fuel.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates, generally, to ultra-low sulfurfuel compositions containing organometallic additives and a method ofprotecting emissions systems. Emissions systems as used herein broadlyincludes catalysts and associated equipment which is generally locatedin the effluent stream of a combustion system, e.g. in the exhaust orthe like. The invention contemplates the addition of various compoundsto an ultra low sulfur fuel to protect the emissions systems frompoisoning by exhaust byproducts, and a method of protecting emissionssystems from poisoning from impurities found in the fuel and lubricantsources and increasing the catalyst durability in these systems.

[0003] More specifically, the present invention relates to ultra-lowsulfur fuel compositions containing an organometallic compound whichacts as a scavenger to prevent poisoning deposits such as sulfur,phosphorus or lead on catalytic emissions systems used for reducingtailpipe emissions, thereby contributing to lowered emissionscharacteristics and improved emissions system efficiency, therebycontributing to lowered emissions characteristics and improved emissionssystem efficiency and improved emission hardware (e.g., catalyst)durability.

[0004] 2. Description of the Prior Art

[0005] It is well known in the automobile industry to reduce tailpipeemissions by using various strategies. The most common method forreducing emissions from spark ignition engines is by careful control ofthe air-fuel ratio and ignition timing. For example, retarding ignitiontiming from the best efficiency setting reduces HC and NO_(x) emissions,while excessive retard of ignition increases the output of CO and HC.Increasing engine speed reduces HC emissions, but NO_(x) emissionsincrease with load. Increasing coolant temperature tends to reduce HCemissions, but this results in an increase in NO_(x) emissions.

[0006] It is also known that treating the effluent stream from acombustion process by exhaust after treatment can lower emissions. Theeffluent contains a wide variety of chemical species and compounds, someof which may be converted by a catalyst into other compounds or species.For example, it is known to provide exhaust after treatment including athree-way catalyst and a lean NO_(x) trap. Other catalytic andnon-catalytic methods are also known.

[0007] Thermal reactors are noncatalytic devices which rely onhomogeneous bulk gas reactions to oxidize CO and HC. However, in thermalreactors, NO_(x) is largely unaffected. Reactions are enhanced byincreasing exhaust temperature (e.g. by a reduced compression ratio orretarded timing) or by increasing exhaust combustibles (rich mixtures).Typically, temperatures of 1500° F. (800° C.) or more are required forpeak efficiency. Usually, the engine is run rich to give 1 percent COand air is injected into the exhaust. Thermal reactors are seldom used,as the required setting dramatically reduces fuel efficiency.

[0008] Catalytic systems are capable of reducing NO_(x) as well asoxidizing CO and HC. However, a reducing environment for NO_(x)treatment is required which necessitates a richer than chemicallycorrect engine air-fuel ratio. A two-bed converter may be used in whichair is injected into the second stage to oxidize CO and HC. Whileefficient, this procedure results in lower fuel economy.

[0009] Single stage, three way catalysts (TWC's) are widely used, butthey require extremely precise fuel control to be effective. Only in theclose proximity of the stoichiometric ratio is the efficiency high forall three pollutants, excursions to either side of stoichiometric cancause increase in hydrocarbon and carbon monoxide or NO_(x) emissions.Such TWC systems can employ, for example, either a zirconia or titaniumoxide exhaust oxygen sensor or other type of exhaust sensor and afeedback electronic controls system to maintain the required air-fuelratio near stoichiometric.

[0010] Catalyst support beds may be pellet or honeycomb (e.g.monolithic). Suitable reducing materials include ruthenium and rhodium,while oxidizing materials include cerium, platinum and palladium.

[0011] Diesel systems raise a different set of challenges for emissionscontrol. Strategies for reducing particulate and HC include optimizingfuel injection and air motion, effective fuel atomization at varyingloads, control of timing of fuel injection, minimization of parasiticlosses in combustion chambers, low sac volume or valve cover orificenozzles for direct injection, reducing lubrication oil contributions,and rapid engine warm-up.

[0012] In terms of after treatment, it is known that diesel enginesgenerally bum lean and the exhaust will therefore usually contain excessoxygen. Thus, NO_(x) reduction with conventional three-way catalysts isnot feasible. NO_(x) is removed from diesel exhaust by either selectivecatalytic reduction, the use of lean NO_(x) catalysts such as thosecomprised of zeolitic catalysts or using metals such as iridium, orcatalyzed thermal decomposition of NO into O₂ and N₂.

[0013] Diesel particulate traps have been developed which employ ceramicor metal filters. Thermal and catalytic regeneration can burn out thematerial stored. Particulate standards of 0.2 g/mile may necessitatesuch traps. Both fuel sulfur and aromatic content contribute toparticulate emissions. Catalysts have been developed for diesels whichare very effective in oxidizing the organic portion of the particulate.

[0014] Improved fuel economy can be obtained by using a lean-burngasoline engine, for example, a direct injection gasoline engine,however currently NO_(x) cannot be reduced effectively from oxidizingexhaust using a typical three-way catalyst because the high levels ofoxygen suppress the necessary reducing reactions. Without a NO_(x)adsorber or lean NO_(x) trap (LNT), the superior fuel economy of thelean-burn gasoline engine cannot be exploited. The function of the LNTis to scavenge the NO_(x) from the exhaust, retaining it for reductionat some later time. Periodically, the LNT must be regenerated byreducing the NO_(x). This can be accomplished by operating the engineunder rich air-fuel ratios for the purpose of purging the trap. Thischange in operating conditions can adversely effect fuel economy as wellas driveability. These LNT's may also be placed on diesel engines, whichalso operate in a lean air-fuel mode. As in the lean-burn gasolineengines, the exhaust of both types of engines is net oxidizing andtherefore is not conducive to the reducing reactions necessary to removeNO_(x). It is an object of the present invention to improve the storageefficiency and durability of the LNT and to prolong the useful life ofthe LNT before regeneration is necessary.

[0015] It is well known that NO_(x) adsorbers are highly vulnerable todeactivation by sulfur (see, for example, M. Guyon et al., Impact ofSulfur on NO _(x) Trap Catalyst Activity-Study of the RegenerationConditions, SAE Paper No. 982607 (1998); and P. Eastwood, CriticalTopics in Exhaust Gas Aftertreatment, Research Studies Press Ltd. (2000)pp.215-218.) and other products resulting from fuel combustion andnormal lubricant consumption. The US Environmental Protection Agency(EPA) has set forth proposed rules for limiting the sulfur content ofhighway diesel fuels to a level of 15 parts per million (see 65 FR35429, Jun. 2, 2000, the complete text of which is incorporated hereinby reference). The EPA states “This proposed sulfur standard is based onour assessment of how sulfur-intolerant advanced exhaust emissioncontrol technologies will be.” It is an object of the present inventionto provide fuel or lubricant compositions capable of reducing theadverse impact of sulfur, and other exhaust byproducts, on catalyticemissions control technologies including NO_(x) adsorbers and LNTs.Further, the present invention provides refiners with flexibility incomplying with the objective of said proposed rule by allowing refinersto reduce sulfur to a certain level above the 15 ppm level of the ruleand still obtain the benefits of improved exhaust emissions controltechnology performance obtained by using fuels containing lower levelsof sulfur.

[0016] Performance fuels for varied applications and engine requirementsare known for controlling combustion chamber and intake valve deposits,cleaning port fuel injectors and carburetors, protecting against wearand oxidation, improving lubricity and emissions performance, andensuring storage stability and cold weather flow. Fuel detergents,dispersants, corrosion inhibitors, stabilizers, oxidation preventers,and performance additives are known to increase desirable properties offuels.

[0017] Organometallic manganese compounds, for examplemethylcyclopentadienyl manganese tricarbonyl (MMT), available from EthylCorporation of Richmond, Va., is known for use in gasoline as anantiknock agent (see, e.g. U.S. Pat. No. 2,818,417). These manganesecompounds have been used to lower deposit formation in fuel inductionsystems (U.S. Pat. Nos. 5,551,957 and 5,679,116), sparkplugs (U.S. Pat.No. 4,674,447) and in exhaust systems (U.S. Pat. Nos. 4,175,927,4,266,946, 4,317,657, and 4,390345. Organometallic iron compounds, suchas ferrocene, are known as well for octane enhancement (U.S. Pat.4,139,349).

SUMMARY OF THE INVENTION

[0018] The present invention contemplates supplying, in a spark- orcompression ignition lean, stoichiometric, or rich system, a low sulfurfuel containing a sufficient amount of an organometallic compound, e.g.MMT or the like, to effectively reduce the impact of poisoningsubstances on emissions systems for fuel-combustion systems.

[0019] The combustion of a fuel containing an organometallic manganesecompound, such as MMT, results in mixtures of manganese compoundscontaining, among others, species of manganese oxides, manganesephosphates and manganese sulfates. As used hereinafter, a stoichiometricratio will be referred to using lambda, which is calculated using thefollowing formula:${lambda} = {\frac{{{air}/{fuel}}\quad {ratio}}{{stoichiometric}\quad {{air}/{fuel}}\quad {ratio}}.}$

[0020] When lambda=1, the system is stoichiometric. When lambda>1, ormore preferably>1.02, the system is a lean system. When lambda<1, thesystem is a rich system.

[0021] In a gasoline or diesel engine that is operating with excess airaccording to the present invention, under lean conditions and using afuel containing an organometallic compound according to the presentinvention, the metal will combine with combustion byproducts, e.g.sulfur, to form, e.g., metal sulfates in the exhaust. These compoundsare not stable at the high temperatures found in the exhaust manifold orthose associated around typical three way catalysts. However, at lowertemperatures under which lean NO_(x) catalysts, diesel particulatetraps, continuously regenerating traps, lean NO_(x) traps or dieseloxidation catalysts operate, the metal can scavenge the sulfur and formstable metal sulfate compounds. This scavenging process then ties up thesulfur and protects the catalyst from sulfur deposition. Suitableexhaust temperatures are below 650° C., preferably below 600° C. andmore preferably below about 500° C. For example, from about 200 to about650° C.

[0022] Suprisingly, when a compound according to the present inventionis used in a fuel containing low amounts of sulfur, the conversionefficiency of emissions systems is maintained at a much higher rate thanwhen the base fuel is used alone.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a graphical representation comparing the sulfur contenton a diesel oxidation catalyst aged 80,000 km on base diesel fuel (Base)or additized diesel fuel containing organometallic compounds (Metal).

[0024]FIG. 2 is a graphical representation comparing NO_(x) conversionloss of a lean NOx trap with a spark-ignition base fuel and the basefuel plus an organometallic compound according to the present invention,wherein the base fuel contains 30 ppm sulfur.

[0025]FIG. 3 is a graphical representation comparing NO_(x) conversionof a lean NOx trap after operating 46 hours on a base fuel and a fuelcomposition according to the present invention.

[0026]FIG. 4 is a graphical representation comparing NO_(x) conversionloss of a catalysts with a spark-ignition base fuel and the base fuelplus an organometallic compound according to the present invention,wherein the base fuel contains 30 ppm sulfur.

DETAILED DESCRIPTION

[0027] Catalytic based emissions systems are well known. As exhaustemissions control systems become more advanced and emissionsrestrictions become tighter, the susceptibility of emissions controlsystems to poisoning increases.

[0028] Exhaust emission control systems have a tendency to lose theireffectiveness over time. The present invention contemplates providing anorganometallic compound to a low sulfur fuel composition. Suitableorganometallic compounds include those containing at least one alkali,alkaline earth or transition metal in conjunction with an appropriateligand.

[0029] The fuel compositions of the present invention can furtherenhance the emissions control system protection of the low sulfur fuel.Also, the present invention allows for use of fuels having a highersulfur content to function in a similar manner to a fuel having a lowersulfur content with respect to protecting the exhaust emission controltechnologies.

[0030] Preferred metals include sodium, potassium, calcium, barium,strontium, rhodium, cerium, palladium, platinum, iron, manganese andmixtures thereof. The addition of a variety of organometallic compoundsto fuel compositions is known. Representative organometallic compoundsfor use in the present invention include those compounds taught in U.S.Pat. Nos. 4,036,605; 4,104,036; 4,474580; 4,568,357; 4,588,416;4,674,447; 4,891,050; 4,908,045; 4,946,609; 4,955,331; 5,113,803;5,599,357; 5,919,276; 5,944,858; 6,051,040 and 6,056,792; and EuropeanPatent EP 466 512 B1.

[0031] Especially preferred organometallic compounds are thosecontaining at least one of the metals selected from the group consistingof manganese, iron, strontium, cerium, barium, platinum and palladium.Preferred manganese containing organometallic compound are manganesetricarbonyl compounds delivered in the fuel or through the lubricatingcomposition. Such compounds are taught, for example, in U.S. Pat. Nos.4,568,357; 4,674,447; 5,113,803; 5,599,357; 5,944,858 and EuropeanPatent No. 466 512 B1. Other methods of delivery, including directinjection into the combustion chamber or exhaust, are also suitable forpractice of the instant invention.

[0032] Suitable manganese tricarbonyl compounds which can be used in thepractice of this invention include cyclopentadienyl manganesetricarbonyl, methylcyclopentadienyl manganese tricarbonyl,dimethylcyclopentadienyl manganese tricarbonyl,trimethylcyclopentadienyl manganese tricarbonyl,tetramethylcyclopentadienyl manganese tricarbonyl,pentamethylcyclopentadienyl manganese tricarbonyl, ethylcyclopentadienylmanganese tricarbonyl, diethylcyclopentadienyl manganese tricarbonyl,propylcyclopentadienyl manganese tricarbonyl, isopropylcyclopentadienylmanganese tricarbonyl, tert-butylcyclopentadienyt manganese tricarbonyl,octylcyclopentadienyl manganese tricarbonyl, dodecylcyclopentadienylmanganese tricarbonyl, ethylmethylcyclopentadienyl manganesetricarbonyl, indenyl manganese tricarbonyl, and the like, includingmixtures of two or more such compounds. Preferred are the manganesetricarbonyl compounds which are liquid at room temperature such asmethylcyclopentadienylmanganesetricarbonyl, ethylcyclopentadienylmanganese tricarbonyl, liquid mixtures of cyclopentadienyl manganesetricarbonyl and methylcyclopentadienyl manganese tricarbonyl, mixturesof methylcyclopentadienyl manganese tricarbonyl andethylcyclopentadienyl manganese tricarbonyl, etc.

[0033] Preparation of such compounds is described in the literature, forexample, U.S. Pat. No. 2,818,417, the disclosure of which isincorporated herein in its entirety.

[0034] When formulating fuel compositions of this invention, theorganometallic compounds (e.g., cyclopentadienyl manganese tricarbonylcompounds) are employed in amounts sufficient to reduce the impact ofpoisons, e.g., sulfur, lead and phosphorus, on the emissions systems ofa low sulfur fuel fired engine. Thus the fuels will contain minoramounts of the organometallic compounds sufficient to control the impactof such deposits on catalytic exhaust emission control technologies.Generally speaking, the fuels of the invention will contain an amount ofthe organometallic compound sufficient to provide from about 0.5 toabout 120 mg of metal per liter of fuel, and preferably from about 1 toabout 66 mg of manganese per liter and more preferably from about 2 toabout 33 mg of metal per liter of fuel. When added to the lubricationsystems of automobiles as a means of delivering the metal to the fuelcombustion system, the organometallic concentration will be increased toprovide the above amounts of the metal in the combustion chamber.

[0035] While not wishing to be bound by the following theory, it ispostulated that the sulfur in the fuel reacts with the metal, forexample the manganese in MMT, to form metal sulfate (MSO₄) which arestable in the temperature range of 200-650° C. Surprisingly, metalsulfates such as MnSO₄ do not bind to active sites on the catalystwhereas free sulfur does, in the form of a sulfate.

[0036] When the emissions system contains a component (e.g. abarium-containing lean NO_(x) trap) which is poisonable by combustionproducts, applicants novel compositions and methods provide a substancewhich competes with the active site (e.g. barium) in the low-sulfurfueled engine-out exhaust. So long as the metal of the scavenging agentwill compete with the metal of the catalyst system for complexing withthe sulfur, the metals may be suitable for use as scavenging agents inthe practice of the present invention. The ability of the metalscavenging agent to compete with the metals of the catalyst forcomplexing with the catalyst poisons can be determined by monitoringcatalyst durability. Further, the organometallic scavengers of thepresent invention can reduce the detrimental impact of other poisons,such as phosphorus and lead, on emissions control technologies of thecombustion systems of the present invention.

[0037] It is especially preferred that the sulfur content of the fuel beless than 100 ppm, and the treatment rate of the organometallic compoundbe up to 120 mg/l, more preferably up to 66 mg/l, and most preferably upto 33 mg/l, based upon the amount of metal delivered to the fuelcomposition. Higher rates are possible, but excessive treatment of thefuel stock may be detrimental to proper functioning of the combustionsystem componentry.

[0038] In a combustion engine, normal operation results in thecombustion of the lubricant and additives such as those containingphosphorus or zinc added to the lubricant. In addition to the sulfurpresent in the fuel, the compositions of the present invention interactwith the combustion products of these additives and reduce their adverseimpact on exhaust aftertreatment devices. By preventing deposition, thenovel compositions prevent the compounds, such as phosphorus, fromcovering catalyst or storage sites in the aftertreatment systems andreducing the aftertreatment system's effectiveness. With thecompositions of the present invention, the aftertreatment system'seffectiveness in maintained over extended periods of operation.

EXAMPLES Example 1

[0039] Two vehicles equipped with diesel engines and oxidation catalystswere tested over 80,000 km. One vehicle used diesel fuel. The other useddiesel fuel containing organometallic additives in an amount sufficientto provide 17 ppm calcium and 3 ppm manganese to the fuel. At the end ofmileage accumulation the two catalysts were removed from the vehicle andthe elemental content of these catalysts was evaluated. As seen in FIG.1, the catalysts from the vehicle operated on a fuel containingorganometallic scavengers contained lower amounts of sulfur. Thisdemonstrates that use of organometallic compounds scavenges sulfur andprevents it deposition on the catalyst.

Example 2.

[0040] These same diesel catalysts were examined for other catalystpoisons as shown in Table 1 below. The catalyst from the engine operatedaccording to the present invention was found to contain lower amounts ofphosphorus and lead compared to the catalysts from the vehicle usingbase fuel. This scavenging of P and Pb has not been observed in enginesthat run significantly greater air than stoichiometric or in dieselengine applications. The presence of P and Pb on a catalyst would reducecatalyst activity; therefore, the scavenging of these compounds by theadditive should provide greater catalyst durability. TABLE I CATALYSTPOISON CONTENT (ppm) Base Fuel MMT Fuel Catalysts Pb P S Catalysts Pb PS Front in 22 4756 2344 Front in 19.6 1565 812 mid 24 4375 2518 mid 12.81294 331 out 20.9 4303 1812 out 16.6 1046 1586 Rear in 26 4246 2683 Rearin 16.1 1379 1623 mid 25 2094 2543 mid 17.8 944 1111 out 23.8 1361 3098out 17.8 794 965 Average 23.62 3522.5 2499.7 Average 16.78 1170.31071.33

[0041] As may be seen from the above examples, the addition of theorganometallic compound acts to reduce the deposits of P, Pb and S uponthe catalyst structure, thereby enhancing life and maintainingefficiency of the emissions system and reducing overall emissions.

[0042] Such a reduction of deposits on catalysts is unexpected, asheretofore, such catalysts have been suitable only for so-calledstoichiometrically balanced systems, and it is unexpected that anunbalanced system, e.g. a lean fuel combustion system, would work. Ithas been understood that for such three-way catalysts to work, they mustbe exactly matched to the stoichiometry of the combustion system or theproduction of emissions would be above that which is achievable with thepractice of the instant invention.

[0043] Further, the method according to the instant invention isespecially useful in low sulfur fuels, e.g., those with less than 100ppm, preferably 50 ppm or less, more preferably 30 ppm or less, mostpreferably 20 ppm or less, for example 15 ppm or less, sulfur as itenhances the sulfur emissions reduction without the need to resort tomore expensive desulfurization procedures.

[0044] An especially preferred sulfur range in the fuel according to thepresent invention is from about 20 to about 50 ppm sulfur. Thedeleterious effects of other catalyst poisons, including those such asphosphorus and lead are also suitable for reduction according to thepresent invention by providing competing scavengers according to thepresent invention. Thus the advantages of the present invention canstill be recognized with fuels containing ultra-low levels of sulfur,for example 15 ppm or less, 5 ppm or less as well as sulfur-free fuels.

[0045] The base fuels used in formulating the compositions of thepresent invention include base fuels suitable for use in the operationof spark-ignition or compression-ignition internal combustion enginessuch as diesel fuel, jet fuel, kerosene, unleaded motor and aviationgasolines, and so-called reformulated gasolines which typically containboth hydrocarbons of the gasoline boiling range and fuel-solubleoxygenated blending agents, such as alcohols, ethers and other suitableoxygen-containing organic compounds. Oxygenates suitable for use in thepresent invention include methanol, ethanol, isopropanol, t-butanol,mixed C₁ to C₅ alcohols, methyl tertiary butyl ether, tertiary amylmethyl ether, ethyl tertiary butyl ether and mixed ethers. Oxygenates,when used, will normally be present in the base fuel in an amount belowabout 25% by volume, and preferably in an amount that provides an oxygencontent in the overall fuel in the range of about 0.5 to about 5 percentby volume.

[0046] In a preferred embodiment, the middle-distillate fuel is a dieselfuel having a sulfur content of up to about 0.01%, preferably 0.005% orless, more preferably 0.003% or less, by weight, as determined by thetest method specified in ASTM D 2622-98.

Example 3

[0047] A commercial lean NOx trap from a direct injection gasoline (DIG)engine was cored and cut into 1 inch by ¾ inch diameter samples. Acatalyst sample was placed in a 1 inch stainless tube which in turn wasin an electric oven down stream of a pulsed flame combustor. The pulsedflame combustor burned iso-octane with and without MMT. The combustorcycle was 5 min. consisting of 4 min. lean operation to trap NOx (lambda1.3 with NOx added to give 500 ppm to the catalyst), and 1 min. richoperation to reduce the trapped NOx (lambda 0.9 with no added NOx).Typically the catalyst approached saturation with NOx at the end of the4 min. lean period so NOx conversion were measured during the first 1min. of the lean period to give data more representative of a commercialvehicle. The catalyst oven provided a constant catalyst temperature. SO2gas could be added to the combustor to simulate exhaust from a 30 ppmsulfur fuel.

[0048] Turning now to FIGS. 2 and 3, experimental data from a leanNO_(x) trap evidences the beneficial properties of the presentinvention. The experimental protocol was as follows: exhaust gas from a30 ppm sulfur equivalent fuel was run over the lean NO_(x) catalysts for46 hours with the catalyst temperature 350C. The NO_(x) conversion wasmeasured constantly throughout the test. The MMT fuel contained MMT at18 mg Mn/liter. Reported conversion was calculated for the first 1minute at lean operation. The loss in NO_(x) conversion on an hourlybasis is substantially higher for non-MMT containing fuels.

[0049]FIG. 2 illustrates the deterioration rate for NO_(x) conversion.Conversely, this could be looked upon as the rate of sulfur poisoning ofthe conversion process. As can be seen from this data, MMT at 18 mgMn/liter protected the catalyst from sulfur poisoning and resulted in adeterioration rate that was only 80% of that observed from base fuelwithout MMT.

[0050]FIG. 3 illustrates the lean NO_(x) Trap NO_(x) efficiency at theend of test for several temperatures. The LNT operated on a fuelcontaining MMT displayed higher activity across a range of temperatures.

[0051]FIG. 4 illustrates the deterioration rate for NOx conversion withfour separate catalyst samples from the same catalyst. Samples #1 and #2utilized base fuel and samples #3 and #4 utilized a fuel containing MMT.Both samples with MMT showed lower deterioration rates. Since thedifferences in deterioration rates are much greater than the 95%confidence limits, these differences are considered statisticallysignificant.

[0052] The present invention is suitable for use in all combustionsystems including burners and large and small engines, such as 4 strokeand 2 stroke engines, e.g. those in generators, leaf blowers, trimmers,snow blowers, marine engines, or other types of engines which may havethe scavenger delivered to the combustion chamber. The scavenger iseffective in the effluent stream of an exhaust system, especially wherethe emissions control is downstream from the combustion system.

[0053] It is to be understood that the reactants and components referredto by chemical name anywhere in the specification or claims hereof,whether referred to in the singular or plural, are identified as theyexist prior to coming into contact with another substance referred to bychemical name or chemical type (e.g., base fuel, solvent, etc.). Itmatters not what chemical changes, transformations and/or reactions, ifany, take place in the resulting mixture or solution or reaction mediumas such changes, transformations and/or reactions are the natural resultof bringing the specified reactants and/or components together under theconditions called for pursuant to this disclosure. Thus the reactantsand components are identified as ingredients to be brought togethereither in performing a desired chemical reaction (such as formation ofthe organometallic compound) or in forming a desired composition (suchas an additive concentrate or additized fuel blend). It will also berecognized that the additive components can be added or blended into orwith the base fuels individually per se and/or as components used informing preformed additive combinations and/or sub-combinations.Accordingly, even though the claims hereinafter may refer to substances,components and/or ingredients in the present tense (“comprises”, “is”,etc.), the reference is to the substance, components or ingredient as itexisted at the time just before it was first blended or mixed with oneor more other substances, components and/or ingredients in accordancewith the present disclosure. The fact that the substance, components oringredient may have lost its original identity through a chemicalreaction or transformation during the course of such blending or mixingoperations is thus wholly immaterial for an accurate understanding andappreciation of this disclosure and the claims thereof.

[0054] At numerous places throughout this specification, reference hasbeen made to a number of U.S. Patents and published foreign patentapplications. All such cited documents are expressly incorporated infull into this disclosure as if fully set forth herein.

[0055] This invention is susceptible to considerable variation in itspractice. Therefore the foregoing description is not intended to limit,and should not be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

[0056] Patentee does not intend to dedicate any disclosed embodiments tothe public, and to the extent any disclosed modifications or alterationsmay not literally fall within the scope of the claims, they areconsidered to be part of the invention under the doctrine ofequivalents.

Having described the invention as above, we claim:
 1. A method of enhancing performance durability of a catalytic emissions control system in a fuel combustion system containing a catalytic device having a transition metal, alkali or alkaline earth metal element, or combinations thereof (catalytic elements), said combustion system producing at least one byproduct, comprising: supplying a fuel containing 100 ppm or less sulfur to said fuel combustion system, said combustion system being provided with a scavenger, said scavenger complexing with at least one combustion byproduct, said scavenger being supplied in an effective amount to complex with the at least one fuel combustion byproduct, whereby the impact of said fuel combustion byproduct on said emissions control system are reduced.
 2. The method of claim 1, wherein said fuel contains 50 ppm or less sulfur.
 3. The method of claim 2, wherein said fuel contains 30 ppm or less sulfur.
 4. The method of claim 3, wherein said fuel contains 20 ppm or less sulfur.
 5. The method of claim 4, wherein said fuel contains 15 ppm or less sulfur.
 6. The method of claim 1, wherein said fuel comprises a spark-ignition fuel.
 7. The method of claim 1, wherein said fuel comprises a compression-ignition fuel.
 8. A method as claimed in claim 1, wherein the scavenger is an organometallic compound.
 9. A method as claimed in claim 8, wherein the scavenger includes at least one metal selected from the group consisting of magnesium, manganese, barium, cerium, strontium, iron, calcium, platinum, palladium and mixtures thereof.
 10. A method as claimed in claim 8, wherein the scavenger comprises at least one alkali and/or alkaline earth metal.
 11. A method as claimed in claim 8, wherein the scavenger comprises at least one transition metal.
 12. A method as claimed in claim 11, wherein said organometallic compound at least one manganese tricarbonyl compound.
 13. A method as claimed in claim 1, wherein the scavenger is present in an amount so as to provide from 0.5 to about 120 mg of metal per liter of fuel.
 14. A method as claimed in claim 13, wherein the scavenger is present in an amount so as to provide from about 1 to about 66 mg of metal per liter of fuel.
 15. A method as claimed in claim 1, wherein the combustion system operates at a lambda>1.2.
 16. A method as claimed in claim 1, wherein the emissions reduction system comprises a catalytic convertor.
 17. A method as claimed in claim 1, wherein the emissions reduction system comprises a lean NO_(x) trap.
 18. A method as claimed in claim 1, wherein the catalytic device comprises barium.
 19. An apparatus for reducing emissions control system poisoning in a lean fuel combustion system having a stream of effluent, comprising: a combustion system which operates at a lambda>1, a base fuel containing 100 ppm or less sulfur, and present, in an effective amount to complex with at least one combustion byproduct in the effluent stream, a scavenger.
 20. The apparatus of claim 19, wherein the base fuel contains 50 ppm or less sulfur.
 21. An apparatus as claimed in claim 19, wherein the scavenger comprises at least one organometallic compound.
 22. An apparatus as claimed in claim 21, wherein the organometallic compound comprises at least one manganese tricarbonyl compound.
 23. An apparatus as claimed in claim 19, wherein the scavenger comprises at least one element selected from the group consisting of transition metal elements.
 24. An apparatus as claimed in claim 19, wherein the scavenger comprises at least one metal selected from the group consisting of magnesium, manganese, barium, cerium, strontium, iron, calcium, platinum, palladium and mixtures thereof.
 25. An apparatus as claimed in claim 19, wherein the fuel comprises a compression-ignition fuel and the emissions control system comprises at least one member selected from the group consisting of an oxidation catalyst, a three-way catalyst, a catalyzed particulate trap, exhaust gas sensors and a lean NO_(x) trap.
 26. An apparatus as claimed in claim 19, wherein the fuel comprises a spark-ignition fuel and the emissions control system comprises at least one member selected from the group consisting of an oxidation catalyst, a three-way catalyst, exhaust gas sensors and a lean NO_(x) trap.
 27. A catalytic emissions control system for the after treatment of a combustion process exhaust stream, comprising: an exhaust passageway for the passage of an exhaust stream containing exhaust byproducts from the combustion of a fuel, at least one catalytic material having catalytic activity, said catalytic material being located within the exhaust passageway and contacting the exhaust stream, wherein the exhaust stream contains a scavenger which complexes with at least one of the exhaust byproducts and reduces the impact of the byproduct upon the catalytic material, and wherein said fuel contains 100 ppm or less sulfur.
 28. An emissions system as claimed in claim 27, wherein the scavenger comprises an organometallic compound.
 29. An emissions system as claimed in claim 27, wherein the scavenger comprises at least one manganese tricarbonyl compound.
 30. An emissions system as claimed in claim 27, wherein the combustion exhaust byproducts comprises sulfur. 